Projection of strong coupling interaction with thermal bath in a polymer

TL;DR

This paper explores how shifting the boundary between a polymer system and its environment affects the observed stochastic dynamics, revealing the emergence of elastic forces and heat transfer through a boundary-dependent perspective.

Contribution

It introduces a novel boundary-shift approach to analyze stochastic polymer dynamics, highlighting the impact of boundary choice on observed forces and thermodynamics.

Findings

Colored noise induces elastic forces in tagged monomers.

Boundary shifts alter the observed heat transfer and stochastic behavior.

Projection of internal degrees of freedom relates to fluctuation theorem.

Abstract

We investigate modifications of a stochastic polymer picture through a shift in the boundary between the system and an external environment. A conventional bead-and-spring model serving as the coarse-graining model is given by the Langevin equation for all the monomers subject to white noise. However, stochastic motion for only a tagged monomer is observed to occur in the presence of colored noise. The qualitative change in the observations arises from the boundary shift decided by the observer. The Langevin dynamics analyses interpret the colored noise as the emergence of the polymeric elastic force, resulting in additional heat in the tagged monomer observation. Being distinguished from coarse-graining based on scale separation, the projection of comparable internal degrees of freedom is also discussed in light of the fluctuation theorem and the stochastic polymer thermodynamics.